1. Field of the Invention
The present invention is directed to a structural joint system, and to the joining of structural members in frame-forming relation, in particular, to frames having dis-assemblable mechanical joints.
2. Description of the Prior Art
Metal members are widely used in fabricating structures, wherein a variety of structural sections are cut to length and joined to form a framework.
Such frames have a wide range of uses, ranging from knock-down shelving to frames for mounting machine tools, conveyors, etc.
One such knock-down system uses structural members consisting of a semi-enclosed C-section track having T-bolts slidably anchored within the section such that the bolt protrudes, to form an attachment anchor point.
One problem with such knock-down framing is the protrusion of bolt heads at the corners of the frame, which constitute a hazard to personel walking past, who can cut and scratch themselves and catch and tear their clothing on the projecting bolt or the nut head.
Another widely used method consists of joining the frame members by welding. This is time consuming and labour intensive, and provides a rigid, unitary construction quite unsuited for transportation, being space-consuming, and totally unsuited to knock-down and reassembly.
The present invention provides a section-joining joint system for joining rigid sections in disassembable relation, enabling the provision of knock-down assemblies, such as frames, stands and the like.
The subject joint utilizes the piercing of at least one of the joint members, and the application of a single tension member in the form of a bolt and nut in joining relation between the adjoined members. A round-headed carriage bolt with locking head portion may be used, where the bolt locking head portion is located within a corresponding square recess, to rotationally lock the bolt. In one embodiment, the inward piercing operation, carried out on the web portion of the U-section rail, provides a perforated, projecting flap located between the section flanges adjacent the end of the rail, and positioned to receive the tension member, a carriage bolt, in entered relation therethrough. The bolt is inserted inwardly through apertures in the adjoining structural members and the flap perforation, enabling a nut to be applied and pulled tight against the back of the flap, tensioning the bolt, which compresses the members into mutual compressive relation, to complete the joint, while generating high friction forces at abutting faces of the joint members.
In the case of U-section members, which are generally awkward to bolt together, the subject system enables the joining of three such members in mutually joined relation as a stable three-dimensional structure.
In some instances, the orientation of the bolt may not be critical, due to the protection afforded to any projecting nut/bolt portions by the outstanding flange portions of the outermost U-section.
The system advantageously incorporates carriage bolts as the tensioning member, wherein the square-sectioned inner portion of the bolt head is housed within a sized, square recess punched in the outermost U-section. This ensures that only the rounded head portion of the carriage bolt, which is substantially flush, protrudes above the external surfaces of the joint. The punching of the square recess is an economical operation in a production line, while the immobilization of the bolt head minimizes labour and skill requirements for assembling and dis-assembling such joints, as the bolt is immobilized against rotation, such that the nut can be readily tightened or slackened.
The subject system may also be advantageously used with L-section angle-iron members, and combinations of different sections.
Thus there is provided a three-dimensional framework, at least one of the joints thereof having a single tensioned member securing the members of the joint in mutually compressive relation.
The tensioned member is secured by way of an aperture in a projecting web portion, struck from one of the members, to receive the nut of a tensioned bolt member in anchored relation therewith.
In the case of a frame including U-section members in joined relation, the end of one U-section is entered into the U-portion of an adjoining section, whereby adjacent portions of the members restrain each other against relative rotational movement about the tensioned member.
In one U-section frame embodiment having U-section rail portions entered within the xe2x80x9cUxe2x80x9d of the adjoining leg section, the adjoining cross member of the frame joint is positioned having its intermediate web portion backed onto the outer face of the web portion of the leg section.
If desired, this arrangement then permits the introduction of a flat diagonal cross-tie member, sandwiched between the cross member and the leg section.
In another embodiment, it is contemplated that the flange ends of the U-section cross member are relieved by the width of the U-section, and the flanges positioned inwardly, so that the relieved flange ends abut the side of the adjoined leg section, thereby locking the framework in rigid three-dimensional fixed relation.
The locking of a frame may also be achieved by way of an asymetrical joint combination. Thus, in a frame having four leg members, two rail members, and two cross members, the members are jointed by striking out a single flap from one end of each of the rails and cross members, and providing an aperture to receive a bolt member at the other end of each of the members. In the case where carriage bolts are used, such apertures are preferably made square, to receive and engage the square underhead portion of the carriage bolt. The adjoining leg members of each joint are provided with an aperture to receive the carriage bolt.
On assembling a frame, a first corner joint is formed, having a rail member with a flapped end inserted in the U of the leg, which is pressed against the rail-end by the tensioned bolt acting against the cross member, which is located outside the leg. For this corner the rail section maintains the leg in a vertical orientation, against lateral forces acting on the frame.
The adjacent second corner joint, having a cross member with a flapped end inserted in the U of the leg, has a rail member compressed against the flange portion of the leg by the tensioned bolt, serving to vertically stabilize the leg, by way of the cross member, against longitudinal forces acting upon the frame.
In this manner, the frame is stabilized laterally by the first joint and longitudinally by the second joint. This stabilization may be repeated in similar fashion at the other end of the frame, such that the respective flap/rail joints are diagonally across from each other, and similarly, the flap/cross member joints are diagonally across from each other. This particular form of asymetry has the particular advantage that each member of a frame (rails and cross members) receives the same flap and aperture treatment, thereby rendering assembly correspondingly straightforward.
It will be understood that other asymetric arrangements can be readily arranged. Thus, the punched-out flap or tongue can be provided at one or both ends of a member, and the other members of a respective joint may be accordingly perforated to receive the square head of a carriage bolt, or the barrel portion of a bolt in inserted relation.
The tension member may be a carriage or other type of bolt. However, the rounded head of the carriage bolt, and its self-locking square inner head portion, in conjunction with a punched square bolt hole to receive and lock that head against rotation, provides a combination that greatly facilitates assembly, with minimal skills and effort, the nut being readily accessible, on the inner face of the web flap.
The perforation for the bolt, in the punched-out web flap is preferably located closely adjacent the web, thereby minimizing the bending moment that is applied against the flap, when the bolt is tensioned. The aperture left by the flap facilitates insertion of the nut on the end of the carriage bolt. A spacer may be positioned about the bolt, in supporting relation with the web flap, to limit or prevent deformation of the flap by the tensioning of the bolt.
While in the preferred embodiment the flap strike-out is located in spaced relation from the end of the joint member, the flap strike-out can extend to the end of the member in some circumstances.
Uses of the subject join system are virtually unlimited, and include framework for shelving, desks, platforms, seats, foot rests, chairs, scaffolding, stairways, decks, ramps, walkways, partitions, ladders, bracing""s, conveyor supports and frame rail, miscellaneous furniture, picnic tables, buildings, etc.